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Full text of "Handbook Of Chemical Engineering - I"

PYROMETRY
435
each. Assume that both instruments are calibrated to read correctly when connected separately to any couple. The potential drop E across the terminals of either instrument bears the following relation to e the electromotive force of the couple.
The scale of the instrument is graduated to take account of this reduction motive force.    When the two instruments are connected in parallel, tl
Thermocouple
Gas Pipe Driven In Ground
Junction of Extension "Wire am
Copper Lauds to lusLrumont
Soldered and Insulated
FIG. 11.—Rare-metal couple installed.
Becording
Instrument
in Office
>°<M

J                u                 v
FIG. 12.—Multiple installation for five thermocouples.
drop across the indicator and recorder is given by the following equation where R = resistance of indicator or recorder and r — line resistance.
P/         Re        50°
*   -R + fr-m*
There is accordingly a reduction in electromotive force by the factor 500/506 when the instruments are connected in parallel to the same couple.    Each instrument is